Internet Draft                               Hang Liu 
          draft-liu-gmpls-ospf-restoration-00.txt      Dimitrios Pendarakis 
          Expires: April 2003                          Bala Rajagopalan 
                                                       Nooshin Komaee 
                                                       Tellium, Inc. 
                                                       October 2002 
           
              OSPF-TE Extensions in Support of Shared Mesh Restoration 
                                           
                      <draft-liu-gmpls-ospf-restoration-00.txt> 
            
          Status of this Memo  
              
             This document is an Internet-Draft and is in full conformance 
             with all provisions of Section 10 of RFC2026. 
              
             Internet-Drafts are working documents of the Internet 
             Engineering Task Force (IETF), its areas, and its working 
             groups.  Note that other groups may also distribute working 
             documents as Internet-Drafts.  
                  
             Internet-Drafts are draft documents valid for a maximum of six 
             months and may be updated, replaced, or obsoleted by other 
             documents at any time. It is inappropriate to use Internet-
             Drafts as reference material or to cite them other than as 
             "work in progress."  
                  
             The list of current Internet-Drafts can be accessed at  
             http://www.ietf.org/ietf/1id-abstracts.txt  
              
             The list of Internet-Draft Shadow Directories can be accessed 
             at http://www.ietf.org/shadow.html.  
                  
          Abstract  
              
             This document describes extensions to the OSPF-TE routing 
             protocol in support of path computation for shared mesh 
             restoration. New optional sub-TLVs are added to the link TLV 
             of the Traffic Engineering (TE) LSA so that the sharing 
             information of the restoration resource on the TE link 
             reserved for shared mesh restoration is disseminated. The 
             extensions supports both SRLG-disjoint and node-disjoint 
             paths.  





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          1. Introduction  
               
             In shared mesh restoration [1,2,3,4], the restoration LSP is 
             pre-computed and its resource is reserved along the path 
             through signaling protocols [5, 6, 7]. However no cross-
             connections are performed along the restoration path. The 
             complete establishment of the restoration LSP occurs only 
             after the working LSP fails, and requires some additional 
             signaling. The common restoration resource reserved at a node 
             or on a TE link may be shared by multiple restoration LSPs to 
             restore multiple working LSPs. In order to avoid contention 
             for the reserved restoration resource (bandwidth or channel) 
             during a single SRLG/node failure, two restoration LSPs may 
             share the common reserved restoration resource only if their 
             respective working LSPs are mutually SRLG/node disjoint. One 
             failure then does not disrupt both working LSPs 
             simultaneously.  
              
             Shared mesh restoration achieves efficient utilization of 
             network resources by sharing the restoration resource. It can 
             achieve reasonably fast switching time and guarantees 
             successful recovery from a single SRLG/node failure. 
             The resource reserved for restoration can even be used by the 
             other path to carry the extra traffic during normal operation 
             mode (i.e. while there are no failure on the working LSPs). Of 
             course, the restoration path needs to be activated when the 
             working path fails. It may result in a switching time longer 
             than the dedicated 1+1 protection. Furthermore, since multiple 
             restoration LSPs may share the common reserved restoration 
             resource. The contention may occur on the reserved restoration 
             resource when more than one of the working paths fails 
             simultaneously due to multiple failures.  
              
             This document specifies extensions to OSPF [8] in support of 
             carrying link state information for the path computation for 
             shared mesh restoration. It is based on the existing OSPF 
             routing extensions required to support Traffic Engineering and 
             GMPLS [9, 10, and 11]. Similar extensions described here can 
             also be made to IS-IS. These extensions are initially focused 
             on transport networks; however they are not meant to be 
             exclusively for the transport networks. 




           
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          2. Required Information 
           
             In shared mesh restoration, multiple restoration LSPs can 
             share the same reserved restoration resource on their common 
             TE links only if the sets of SRLGs and/or nodes traversed by 
             their respective working LSPs are disjoint in order to 
             guarantee recovery from a single SRLG failure or a single node 
             failure. This imposes additional constraints on the path 
             computation. To compute the restoration LSP for the shared 
             mesh restoration, the path computation module needs to have 
             the restoration resource sharing information on the links in 
             the network. In general, the more detail information is 
             available, the better results the path computation algorithms 
             can achieve. On the other hand, in order to reduce the amount 
             of information handled by OSPF and improve the routing 
             scalability, it may be desirable to aggregate the information 
             on a TE link (bundle) [12]. To support path computation for 
             shared mesh restoration, all or some information below can be 
             disseminated by routing protocol. 
           
             (1)  Summarized information about the restoration resource 
             sharing on a TE link for shared mesh restoration, such as the 
             total number of restoration LSPs sharing the restoration 
             resource reserved on the TE link for shared mesh restoration, 
             the total number of SRLGs recovered by the reserved 
             restoration resource on the TE link, the total number of nodes 
             recovered by the reserved restoration resource on the TE link, 
             the total sharable restoration bandwidth at each priority 
             level. 
              
             (2)  The list of SRLGs recovered by the reserved restoration 
             resource on the TE link and their respective sharable 
             restoration bandwidth if the SRLG-disjointness is required to 
             guarantee recovery in the event of a single SRLG failure. 
              
             (3)  The list of nodes recovered by the reserved restoration 
             resource on the TE link and their respective sharable 
             restoration bandwidth if the node-disjointness is also 
             required to guarantee recovery in the event of a single node 
             failure. By distinguishing node failure restoration from SRLG 
             failure restoration, it provides the network operator with 
             options to offer different levels of services and uses the 




           
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             network resource more efficiently as explained later in this 
             section.  
           
             The list of SRLGs/nodes recovered by the TE link is defined as 
             the union of SRLGs/nodes traversed by all the working LSPs 
             whose respective restoration LSPs share the reserved 
             restoration resource on this TE link. The common reserved 
             restoration resource (e.g. an OC-48 channel) can be reused by 
             a restoration LSP to recover a working LSP if no SRLG/node 
             passed over by its working LSP appears in the list of 
             SRLGs/nodes already recovered by the restoration resource. The 
             sharable restoration bandwidth for a SRLG and/or node 
             indicates the available restoration bandwidth on the TE link 
             that can be reserved for recovering this SRLG/node failure. If 
             a working LSP only traverses one SRLG, the available 
             restoration bandwidth that its restoration LSP can share on 
             this TE link is the sharable restoration bandwidth for this 
             SRLG. When a working LSP traverses multiple SRLGs, the 
             sharable restoration bandwidth available for its restoration 
             LSP may become smaller on this TE link. It is the same case 
             for a given node when the node-disjointness is required.  
              
             The total sharable restoration bandwidth is the bandwidth 
             reserved on the TE link for restoration, which is the union of 
             the sharable restoration bandwidth for all SRLGs and nodes. 
              
             A lot of equipment has its own recovery and high availability 
             requirements. The operator may choose to guarantee recovery 
             only from a single SRLG failure or from a SRLG/node failure 
             based on the requirements of the end user applications. For 
             example, an application requires 99.999% availability. The 
             node can meet this requirement because it has its own 
             equipment recovery mechanism. However the fiber links cannot 
             meet this requirement. In order to meet the application 
             availability requirements, the shared mesh restored LSP 
             carrying this application traffic must guarantee recovery from 
             a single SRLG failure, but it does not have to guarantee 
             recovery from a single node failure. Then the common 
             restoration resource can be reserved to restore two working 
             LSPs that traverse a common node (no node-disjoint constraint);  
             i.e. less constraints are required to compute the restoration   
             path.By distinguishing node failure recovery guarantee and SRLG  
             failure recovery guarantee, the operators can offer different  




           
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             levels of services based on performance requirements of the end  
             user applications and utilize the network resource more 
             efficiently.  
           
          3. OSPF Extensions to Support Path Computation for Shared Mesh 
             Restoration 
           
             It is desirable to carry the sharing information of the 
             restoration resource on a TE link with the OSPF so that the 
             information may be used by the path computation algorithm to 
             compute the restoration path for shared mesh restoration. This 
             section specifies the extensions to OSPF-TE in support of 
             shared mesh restoration.  
              
             OSPF traffic engineering extensions [9] and GMPLS extensions 
             [10,11] make use of the Opaque LSA [13]. An Opaque LSA, called 
             Traffic Engineering LSA is defined to carry the additional 
             attributes related to traffic engineering and GMPLS links. The 
             information in the TE LSAs can be used to build an extended TE 
             link state database just as router LSAs are used to build a 
             regular link state database. The extensions here are based 
             upon the OSPF-TE and GMPLS extensions, specifically, we add 
             the following sub-TLVs to the link TLV of the TE LSA. 
           
          3.1 Restoration Information Summary 
           
             Restoration Information Summary sub-TLV specifies the sharing 
             information of the restoration resource reserved for shared 
             mesh restoration on the TE link. The format of the Restoration 
             Information Summary sub-TLV is as follows 
              
           
           
           
           
           
           
           
           
           
           




           
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           0                   1                   2                   3           
           0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
          |         Type(TBA)           |         Length                  | 
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
          | #Shared Restoration LSPs      |       #SRLGs recovered        | 
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
          |   #Nodes recovered            |       Reserved           | 
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
          |      Total Sharable Restoration Bandwidth at priority 0       | 
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
          |      Total Sharable Restoration Bandwidth at priority 1       | 
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
          |      Total Sharable Restoration Bandwidth at priority 2       | 
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
          |      Total Sharable Restoration Bandwidth at priority 3       | 
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
          |      Total Sharable Restoration Bandwidth at priority 4       | 
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
          |      Total Sharable Restoration Bandwidth at priority 5       | 
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
          |      Total Sharable Restoration Bandwidth at priority 6       | 
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
          |      Total Sharable Restoration Bandwidth at priority 7       | 
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
              
             Type: 16 bits 
                   The type of this sub-TLV is TBA. 
              
             Length: 16 bits 
                   The length of this sub-TLV is 40 octets. 
              
             #Shared Restoration LSPs: 16 bits 
                   This field indicates the number of restoration LSPs 
                   sharing the bandwidth reserved for the mesh restoration 
                   on this TE link. 
              
              
              
             #SRLGs recovered: 16 bits 






           
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                   This field indicates the number of SRLGs recovered by 
                   the TE link. The SRLGs here includes all distinct SRLGs 
                   traversed by all the working LSPs whose respective 
                   restoration LSPs shares the reserved restoration 
                   bandwidth on this TE link. Zero means that this 
                   information is not available. 
              
             #Nodes recovered: 16 bits 
                   This field indicates the number of nodes recovered by 
                   the TE link. The nodes here include all distinct nodes 
                   traversed by all the working LSPs whose respective 
                   restoration LSPs shares the reserved restoration 
                   bandwidth on this TE link. Zero means that this 
                   information is not available. 
              
             Total Sharable Restoration Bandwidth at priority 0-7: 32 bits 
                   Total Sharable Restoration Bandwidth specifies the 
                   bandwidth that has been allocated for shared mesh 
                   restoration at each of the eight priority levels. The 
                   bandwidth might have been reserved by one or more shared 
                   restoration LSP. It is encoded in the IEEE floating 
                   point format, with 4 octets per priority. 
              
             The Restoration Information Summary sub-TLV is optional and if 
             a LSA doesnÆt carry the Restoration Information Summary sub-
             TLV, then it means that the information is unknown. 
           
          3.2 SRLG Sharable Restoration Bandwidth 
           
             SRLG Sharable Restoration Bandwidth sub-TLV identifies the 
             sharable restoration bandwidth range for a SRLG on this TE 
             link. By allowing to specify a range instead of a fixed value, 
             it may reduce the amount of information handled by the routing 
             protocol. If the lower bound is equal to the upper bound of 
             the range, it indicates a fixed value of the sharable 
             restoration bandwidth. Its format is as follows 
           
           
           
           
           
           





           
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           0                   1                   2                   3       
           0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
          |         Type(TBA)           |         Length                  | 
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
          |  Priority     |               Reserved                        | 
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
          |      Sharable Restoration Bandwidth Lower Bound               | 
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
          |      Sharable Restoration Bandwidth Upper Bound               | 
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
          |                        SRLG 1                                 | 
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
          |                      ... ...                                  | 
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
          |                        SRLG N                                 | 
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
           
           
               Type: 16 bits 
                    The type of this sub-TLV is TBA. 
           
               Length: 16 bits 
                    The length of this sub-TLV is the length of value field 
                    in octets. 
           
               Priority: 8 bits 
                    This field indicates the priority of sharable 
                    restoration bandwidth. The SRLG sharable restoration 
                    bandwidth can be encoded per priority. If the SRLG 
                    sharable restoration bandwidth is not encoded per 
                    priority, the value of the priority field is set to 
                    0xFF, which means the sharable restoration bandwidth is 
                    the same for all priorities.  
           
               Sharable Restoration Bandwidth Lower Bound and Upper Bound: 
               32 bits 





           
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                    The Sharable Restoration Bandwidth Lower Bound and 
                    Sharable Restoration Bandwidth Upper Bound specify a 
                    range for sharable restoration bandwidth. The sharable 
                    restoration bandwidth for each of SRLG in the following 
                    list falls into this range, i.e. Sharable Restoration 
                    Bandwidth Lower Bound <= sharable restoration bandwidth 
                    for SRLG N < Sharable Restoration Bandwidth Upper 
                    Bound. If the lower bound is equal to the upper bound, 
                    a fixed value of sharable restoration bandwidth is 
                    specified and the sharable restoration bandwidth for 
                    each of SRLGs in the following list is equal to this 
                    value. 
           
               SRLG: 32 bits 
                    The value is a list of 32-bit numbers, each of number 
                    identifies a SRLG.  
                     
             The SRLG Sharable Restoration Bandwidth sub-TLV is optional 
             and if a LSA doesnÆt carry any SRLG Sharable Restoration 
             Bandwidth sub-TLV, then it is assumed that the information is 
             unknown. There may be more than one SRLG Sharable Restoration 
             Bandwidth sub-TLVs in the LSA. However if there are one or 
             more SRLG Sharable Restoration Bandwidth sub-TLVs in the LSAs, 
             the sharable restoration bandwidth for the SRLGs not listed in 
             these SRLG sharable restoration bandwidth sub-TLVs is assumed 
             to be equal to the total sharable restoration bandwidth at 
             that priority on this TE link. 
           
          3.3 Node Sharable Restoration Bandwidth 
           
             Node Sharable Restoration Bandwidth sub-TLV identifies the 
             sharable restoration bandwidth range that is reserved on this 
             TE link for sharing by restoration LSPs to recover a node 
             failure on their working path. It can be used by the path 
             computation algorithms to compute the restoration LSP when it 
             is required that multiple restoration LSP can share the common 
             restoration resource on their common TE links only if their 
             respective working LSPs are node disjoint. Its format is as 
             follows 
           
                




           
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           0                   1                   2                   3 
           0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
          |         Type(TBA)           |         Length                  | 
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
          |  Priority     |               Reserved                        | 
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
          |       Sharable Restoration Bandwidth Lower Bound              | 
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
          |       Sharable Restoration Bandwidth Upper Bound              | 
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
          |                        Node1 ID                               | 
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
          |                      ... ...                                  | 
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
          |                        NodeN ID                               | 
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
           
           
               Type: 16 bits 
                    The type of this sub-TLV is TBA. 
           
               Length: 16 bits 
                    The length of this sub-TLV is the length of value field 
                    in octets. 
           
               Priority: 8 bits 
                    This field indicates the priority of sharable 
                    restoration bandwidth. The node sharable restoration 
                    bandwidth can be encoded per priority. If the node 
                    sharable restoration bandwidth is not encoded per 
                    priority, the value of the priority field is set to 
                    0xFF, which means the sharable restoration bandwidth is 
                    the same for all priorities.  
           
               Sharable Restoration Bandwidth Lower Bound and Upper Bound: 
               32 bits 





           
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                    The Sharable Restoration Bandwidth Lower Bound and 
                    Sharable Restoration Bandwidth Upper Bound specify a 
                    range for sharable restoration bandwidth reserved on a 
                    TE link. The sharable restoration bandwidth for each of 
                    node in the following list falls into this range, i.e. 
                    Sharable Restoration Bandwidth Lower Bound <= sharable 
                    restoration bandwidth for Node N < Sharable Restoration 
                    Bandwidth Upper Bound. If the lower bound is equal to 
                    the upper bound, a fixed value of sharable restoration 
                    bandwidth is specified and the sharable restoration 
                    bandwidth for each of nodes in the following list is 
                    equal to this value. 
           
               Node ID:  32 bits
                    The value is a list of 32-bit numbers, each of number 
                    identifies a node.  
                     
             The Node Sharable Restoration Bandwidth sub-TLV is optional 
             and if a LSA doesnÆt carry any Node Sharable Restoration 
             Bandwidth sub-TLV, then it is assumed that the information is 
             unknown. There may be more than one Node Sharable Restoration 
             Bandwidth sub-TLVs in the LSA. However if there are one or 
             more Node Sharable Restoration Bandwidth sub-TLVs in the LSAs, 
             the sharable restoration bandwidth for the nodes not listed in 
             these Node sharable restoration bandwidth sub-TLVs is assumed 
             to be equal to the total sharable restoration bandwidth at 
             that priority on this TE link. 
           
          4. Acknowledgments 
              
             The authors would like to thank Ramu Ramamurthy, Eric 
             Bouillet, Ahmet Akyamac, Jean-Francois Labourdette, and Sid 
             Chaudhuri for extremely valuable discussions on path 
             computation algorithms and useful input that they have provided 
             in this work.
           
           
           
           
           
           




           
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          5. References 
           
            1. D. Papadimitriou, et al., "Analysis Grid for GMPLS-based 
               Recovery Mechanisms," Internet Draft, work in progress, 
               draft-papadimitriou-ccamp-gmpls-recovery-analysis-00.txt, 
               April 2002. 
            2. E. Mannie, et al., "Recovery (Protection and Restoration) 
               Terminology for GMPLS," Internet Draft, work in progress, 
               draft-mannie-gmpls-recovery-terminology-00.txt, February 
               2002. 
            3. J. P. Lang, B. Rajagopalan, et al., "Generalized MPLS 
               Recovery Functional Specification," Internet Draft, work in 
               progress, draft-bala-gmpls-recovery-functional-00.txt, 
               August, 2002. 
            4. G. Li, et al., "RSVP-TE Extensions for Shared-Mesh 
               Restoration in Transport Networks," Internet Draft, work in 
               progress, draft-li-shared-mesh-restoration-01.txt, November 
               2001. 
            5. P. Ashwood-Smith, et al, "Generalized MPLS - Signaling 
               Functional Description," Internet Draft, work in progress, 
               draft-ietf-mpls-generalized-signaling-08.txt, April 2002. 
            6. P. Ashwood-Smith, et al., "Generalized MPLS û RSVP-TE 
               Extensions," Internet Draft, work in progress, draft-ietf-
               mpls-generalized-rsvp-te-07.txt, April 2002. 
            7. P. Ashwood-Smith, et al., "Generalized MPLS Signaling - CR-
               LDP Extensions," Internet Draft, work in progress, draft-
               ietf-mpls-generalized-cr-ldp-06.txt, April 2002. 
            8. J. Moy, "OSPF Version 2", RFC 2328, April 1998. 
            9. D. Katz, et al., "Traffic Engineering Extensions to OSPF", 
               Internet Draft, work in progress, draft-katz-yeung-ospf-
               traffic-06.txt, October 2001. 
            10. K. Kompella, et al., "Routing Extensions in Support of 
               Generalized MPLS," Internet Draft, work in progress, draft-
               ietf-ccamp-gmpls-routing-04.txt, April 2002. 
            11. K. Kompella, et al., "OSPF Extensions in Support of 
               Generalized MPLS", Internet Draft, work in progress, draft-
               ietf-ccamp-ospf-gmpls-extensions-05.txt, April 2002. 





           
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            12. K. Kompella, et al., "Link Bundling in MPLS Traffic 
               Engineering," Internet Draft, work in progress, draft-
               kompella-mpls-bundle-05.txt, February 2001. 
            13. Coltun, R., "The OSPF Opaque LSA Option," RFC 2370, 
               July 1998. 
             
              
          6. Authors' Addresses 
           
             Hang Liu 
             Dimitrios Pendarakis 
             Bala Rajagopalan 
             Nooshin Komaee 
             Tellium, Inc.   
             2 Crescent Place   
             Oceanport, NJ 07757  
             USA   
             Phone: +1 732 923 4100   
             Email: {hliu, dpendarakis, braja, nkomaee}@tellium.com 
           
           
           
























           
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